20,906 research outputs found
Quantum Reciprocity Conjecture for the Non-Equilibrium Steady State
By considering the lack of history dependence in the non-equilibrium steady
state of a quantum system we are led to conjecture that in such a system, there
is a set of quantum mechanical observables whose retarded response functions
are insensitive to the arrow of time, and which consequently satisfy a quantum
analog of the Onsager reciprocity relations. Systems which satisfy this
conjecture can be described by an effective Free energy functional. We
demonstrate that the conjecture holds in a resonant level model of a multi-lead
quantum dot.Comment: References revised to take account of related work on Onsager
reciprocity in mesoscopics by Christen, and in hydrodynamics by Mclennan,
Dufty and Rub
WHEAT IMPORT DEMAND IN THE JAPANESE FLOUR MILLING INDUSTRY: A PRODUCTION THEORY APPROACH
The translog cost function is used to analyze import demand for wheat differentiated by class and country of origin in the Japanese wheat flour milling industry. Results indicate that U.S. wheat faces strong competition in the Japanese wheat market, but its multiple classes and end-use characteristics enable the United States to preserve the largest market share in Japan.import demand, Japan, wheat, production theory, translog cost function, International Relations/Trade,
Lattice dynamics and electron-phonon coupling in Sr2RuO4
The lattice dynamics in SrRuO has been studied by inelastic neutron
scattering combined with shell-model calculations. The in-plane bond-stretching
modes in SrRuO exhibit a normal dispersion in contrast to all
electronically doped perovskites studied so far. Evidence for strong electron
phonon coupling is found for c-polarized phonons suggesting a close connection
with the anomalous c-axis charge transport in SrRuO.Comment: 11 pages, 8 figures 2 table
Analysing the Security of Google's implementation of OpenID Connect
Many millions of users routinely use their Google accounts to log in to
relying party (RP) websites supporting the Google OpenID Connect service.
OpenID Connect, a newly standardised single-sign-on protocol, builds an
identity layer on top of the OAuth 2.0 protocol, which has itself been widely
adopted to support identity management services. It adds identity management
functionality to the OAuth 2.0 system and allows an RP to obtain assurances
regarding the authenticity of an end user. A number of authors have analysed
the security of the OAuth 2.0 protocol, but whether OpenID Connect is secure in
practice remains an open question. We report on a large-scale practical study
of Google's implementation of OpenID Connect, involving forensic examination of
103 RP websites which support its use for sign-in. Our study reveals serious
vulnerabilities of a number of types, all of which allow an attacker to log in
to an RP website as a victim user. Further examination suggests that these
vulnerabilities are caused by a combination of Google's design of its OpenID
Connect service and RP developers making design decisions which sacrifice
security for simplicity of implementation. We also give practical
recommendations for both RPs and OPs to help improve the security of real world
OpenID Connect systems
Fractal Characterizations of MAX Statistical Distribution in Genetic Association Studies
Two non-integer parameters are defined for MAX statistics, which are maxima
of simpler test statistics. The first parameter, , is the
fractional number of tests, representing the equivalent numbers of independent
tests in MAX. If the tests are dependent, . The second
parameter is the fractional degrees of freedom of the chi-square
distribution that fits the MAX null distribution. These two
parameters, and , can be independently defined, and can be
non-integer even if is an integer. We illustrate these two parameters
using the example of MAX2 and MAX3 statistics in genetic case-control studies.
We speculate that is related to the amount of ambiguity of the model
inferred by the test. In the case-control genetic association, tests with low
(e.g. ) are able to provide definitive information about the disease
model, as versus tests with high (e.g. ) that are completely uncertain
about the disease model. Similar to Heisenberg's uncertain principle, the
ability to infer disease model and the ability to detect significant
association may not be simultaneously optimized, and seems to measure the
level of their balance
The Luminosity Function of high-redshift QSOs - A combined analysis of GOODS and SDSS
Aims: In this work the luminosity function of QSOs is measured in the
redshift range 3.5<z<5.2 for the absolute magnitude interval -21<M_{145}<-28.
The determination of the faint end of the luminosity function at these
redshifts provides important constraints on models of joint evolution of
galaxies and AGNs. Methods: We have defined suitable criteria to select faint
QSOs in the GOODS fields, checking in detail their effectiveness and
completeness. Spectroscopic follow-up of the resulting QSO candidates has been
carried out. The confirmed sample of faint QSOs is compared with a brighter one
derived from the SDSS. We have used a Monte-Carlo technique to estimate the
properties of the luminosity function, checking various parameterizations for
its shape and evolution. Results: Models based on Pure Density Evolution show
better agreement with observation than models based on Pure Luminosity
Evolution. However a different break magnitude with respect to z~2.1 is
required at 3.5<z<5.2. Models with a steeper faint end score a higher
probability. We do not find any evidence for a flattening of the bright end at
redshift z>3.5. Conclusions: The estimated space density evolution of QSOs
indicates a suppression of the formation and/or feeding of Supermassive Black
Holes at these redshifts. The QSO contribution to the UV background is
insufficient to ionize the IGM at 3.5<z<5.2.Comment: 17 pages, 13 ps figures, A&A accepted. Updated to journal versio
Spin-spin correlators in Majorana representation
In the Majorana representation of a spin 1/2 we find an identity which
relates spin-spin correlators to one-particle fermionic correlators. This
should be contrasted with the straightforward approach in which two-particle
(four-fermion) correlators need to be calculated. We discuss applications to
the analysis of the dynamics of a spin coupled to a dissipative environment and
of a quantum detector performing a continuous measurement of a qubit's state
The influence of baryons on the mass distribution of dark matter halos
Using a set of high-resolution N-body/SPH cosmological simulations with
identical initial conditions but run with different numerical setups, we
investigate the influence of baryonic matter on the mass distribution of dark
halos when radiative cooling is NOT included. We compare the concentration
parameters of about 400 massive halos with virial mass from \Msun to
\Msun. We find that the concentration parameters for the
total mass and dark matter distributions in non radiative simulations are on
average larger by ~3% and 10% than those in a pure dark matter simulation. Our
results indicate that the total mass density profile is little affected by a
hot gas component in the simulations. After carefully excluding the effects of
resolutions and spurious two-body heating between dark matter and gas
particles, we conclude that the increase of the dark matter concentration
parameters is due to interactions between baryons and dark matter. We
demonstrate this with the aid of idealized simulations of two-body mergers. The
results of individual halos simulated with different mass resolutions show that
the gas profiles of densities, temperature and entropy are subjects of mass
resolution of SPH particles. In particular, we find that in the inner parts of
halos, as the SPH resolution increases the gas density becomes higher but both
the entropy and temperature decrease.Comment: 8 pages, 6 figures, 1 table, ApJ in press (v652n1); updated to match
with the being published versio
Emergence of intrinsic superconductivity below 1.178 K in the topologically non-trivial semimetal state of CaSn3
Topological materials which are also superconducting are of great current
interest, since they may exhibit a non-trivial topologically-mediated
superconducting phase. Although there have been many reports of pressure-tuned
or chemical-doping-induced superconductivity in a variety of topological
materials, there have been few examples of intrinsic, ambient pressure
superconductivity in a topological system having a stoichiometric composition.
Here, we report that the pure intermetallic CaSn3 not only exhibits topological
fermion properties but also has a superconducting phase at 1.178 K under
ambient pressure. The topological fermion properties, including the nearly zero
quasi-particle mass and the non-trivial Berry phase accumulated in cyclotron
motions, were revealed from the de Haas-van Alphen (dHvA) quantum oscillation
studies of this material. Although CaSn3 was previously reported to be
superconducting at 4.2K, our studies show that the superconductivity at 4.2K is
extrinsic and caused by Sn on the degraded surface, whereas its intrinsic bulk
superconducting transition occurs at 1.178 K. These findings make CaSn3 a
promising candidate for exploring new exotic states arising from the interplay
between non-trivial band topology and superconductivity, e.g. topological
superconductivityComment: 20 pages,4 figure
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